Re: Interesting fail when migrating Pg from Ubuntu Bionic to Focal

On Sun, Mar 06, 2022 at 11:10:00AM -0500, Tom Lane wrote:
> > I tore these boxes down, so can't check immediately, but I think
> > I remember that you're right - single-row queries didn't use JIT.

Got focal box up. Loaded schema for Pg.

Initially select didn't break anything, but when I tuned down
jit_above_cost so that it will kick in - got fails immediately.

> FWIW, I went to the trouble of installing Ubuntu Focal on my
> raspberry pi to see if I could duplicate this, and I couldn't.
> However, what you get from a fresh install now is
> $ dpkg -l | grep libllvm
> ii libllvm10:arm64 1:10.0.0-4ubuntu1 arm64 Modular compiler and toolchain technologies, runtime library
> not 9.0.1. I also found that Fedora 31/aarch64 is still downloadable, and
> that does contain LLVM 9 ... and I could not reproduce it there either.

Soo... plot thickens.

Looks that pg 12 supplied by pgdg required libllvm9:

=$ apt-cache show postgresql-12 | grep -E '^(Package|Version|Depends):'
Package: postgresql-12
Version: 12.9-2.pgdg20.04+1
Depends: ..., libllvm9 (>= 1:9~svn298832-1~), ...

Package: postgresql-12
Version: 12.9-0ubuntu0.20.04.1
Depends: ..., libllvm10 (>= 1:9~svn298832-1~), ...

Package: postgresql-12
Version: 12.2-4
Depends: ..., libllvm10 (>= 1:9~svn298832-1~), ...

Newer pg12 (12.10) from pgdg also depends on llvm9. Perhaps changing the deb to
use/depend-on llvm10 would solve the problem, for now I'm not sure how to do
it. Reached to Christoph about it.

Best regards,

depesz